US2651468A - Self-cycling pneumatic control apparatus - Google Patents

Description

Sept. 8, 1953 F. D. JOESTING 2,651,468

SELF-CYCLING PNEUMATIC CONTROL APPARATUS Filed Nov. 3, 1949' 3 Sheets-Sheet l Bnnentor FREDERICK o. JOESTING attorney S p 3, 3 F. D. JOESTING' 2,651,468

SELF-CYCLING PNEUMATIC CONTROL APPARATUS Filed Nov. 3, 1949 3 Sheets-Sheet 2 FREQERI-CK D. JOESTING Sept. 8, 1953 F. D. JOESTING, 2,651,453

SELF-CYCLING PNEUMATIC CONTROL APPARATUS Filed Nov. 3, 1949 5 Sheets-Sheet 5 Bnventor FREERICK D. JOESTlNG Gttorneg Patented Sept. 8, 1953 SELF- CYCLING PNEUMATIC CONTROL APPARATUS Frederick D. J oesting, Oak Park, Ill., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application November 3, 1949, Serial No. 125,261

16 Claims.

This invention relates to self-cycling pneumatic condition control apparatus.

Some types of conditioning apparatus, especially those normally controlled in an on-off manner such as steam heating systems and spray humidifiers, are difiicult to control satisfactorily under variable loads because of a tendency to overshoot the desired control points. Modulating control is generally satisfactory for heavier loads in two pipe steam heating systems but distribution problems become acute under light load conditions hence this solution is only partially satisfactory and it, of course, cannot be used at all in One pipe systems. Likewise, varying the pressure on the atomizer heads of a humidifier is satisfactory so long as the pressure remains high enough to give good atomizing action; but when the pressure is reduced for lower humidifying loads, the larger drops of water formed are not readily absorbed by the surrounding air, with a consequent wetting of nearby surfaces. The present invention solves these difficulties by causing cyclic operation of the control apparatus, thereby obtaining the benefits of full pressure for the systems involved, and, by varying the relative lengths of the on and 0115 periods, the capacity of the conditioning system is accurately matched with the load. It is therefore an object of this invention to provide an improved time-modulated pneumatic control system.

It is a further object to provide a pneumatic control system capable of cycling action without a separate timer mechanism.

It is another object to provide an improved pneumatic control system capable of maintaining a condition within closer limits than apparatus previously used.

It is an additional object to provide a pneumatic control system for cycling operation wherein the relative length of the on and off periods depends upon whether the condition of the medium being treated is nearer the upper or the lower limits of the operating differential of the system and wherein the system is continuously on or off when said condition is outside the operating differential.

It is a further object to provide a snap acting pneumatic control device having pressure actuated means arranged to relatively slowly adjust the device by an amount exceeding its normal operating differential.

It is a more limited object to provide a bleed type positive acting pneumatic control device including a pneumatic motor means connected v steam,

through a restriction to a branch line passage of the device, said motor means being constructed and arranged to adjust said device and being capable of an adjustment exceeding the normal operating differential of the device.

Even more limited objects provide for positive action pneumatic thermostats, pressure controls, humidistats and the like having pressure actuated means connected through a time delay device to a branch line passage of the apparatus and arranged to adjust the control apparatus sufliciently to cause forced cycling when the condition of the medium being treated is within the normal control range of the apparatus.

While the present invention is best used with pneumatic control apparatus, it is broader than this and may be used with other types of apparatus, hence it is a further object to provide a two-position controller having a normal operating differential and a force exerting adjusting device operable in response to the position of the controller and effective to adjust the controller by an amount exceeding its normal operating differential.

These and other objects will become apparent upon a study of the'following specification and drawings wherein:

Figure 1 is a schematic view of a pneumatic temperature control system incorporating the present invention.

Figure 2 is a partial view of a modification of the thermostat of Figure 1.

Figure 3 is a schematic view of another modification of the thermotsat of Figure 1.

Figure 4 is a schematic view of a pneumatic humidity control system incorporating the present invention.

Figure 5 is another schematic view of the present invention as applied to a pressure controller.

In Figure l, radiator Ill or a conventional onepipe steam heating system is supplied with from a source not shown, through pipe I 5 under the control of valve I2, it being obvious that each radiator of the system may be controlled by an individual valve such as I2, or the several radiators of the system, or of a zone thereof, may be connected in parallel with radiator I0 and under the control of a single valve such as I2. Valve I2 is a conventional one for this service and comprises a valve body I3, a movable valve member I4, a spring I5 and a pneumatic motor I6, spring I5 being arranged to hold member M in an upper open position and motor I6 being arranged to oppose spring I5 and drive Thermostat 22 is basically a conventional snap acting bleed type controller having a base 25, a

nozzle valve member 26, a co-acting valve or nozzle plate 21 carried on pivots 28 (only one being shown) and urged to a nozzle closing position by spring 29. Plate 26 is moved away from its closing position by arm 3| attached to bimetal 32 which in turn is attached to a movable anchor plate 33, said arm 3! extending over the upper edge of plate 21. Anchor member 33, pivoted on pin 34, is adjustable by projecting handle 35 for adjusting the control point of the device, the adjustment being maintained by the friction of the pivotal connection. Bimetal 3.2 is arranged so that it moves arm 3! to the right on a temperature decrease and to the left on a temperature rise, movement to the. right being limited by a stop screw 38 engaging stop flange 39, which is attached to a flanged support member 40, this latter member also serving as the mounting bracket for the elements of the aforementioned nozzle valve assembly.

To insure two-position control of valve plate 2?, and thereby of steam valve l2, a snap acting mechanism is provided comprising a small permanent magnet 41 attached to member 40 and a coacting armature 42 attached to arm 3|, the variations in magnetic attraction between these members varying considerably as armature 42 moves away or toward magnet 4| and thus, in a manner well known in this art, providing snap action of valve plate 21 and causing the controller 22 to have a definite operating diiierential, or change in condition values necessary to move the nozzle plate 21 from one controlling position to the other.

This magnet snap mechanism, as well as the other structural details, are only illustrative for any other snap action mechanism, and other controller details, will work equally well with the present apparatus.

The apparatus thus far described is conventional and works reasonably well excepting that the radiator or radiators tend to overheat before the bimetal 32 can sense an increase in room temperature. This tendency to overheat can be corrected by modulating or proportional control in some heating systems, but this solution is impractical in one-pipe steam systems because a partially closed valve tends to trap condensate in its radiator. Further, with any steam system, distribution difliculties are encountered when the steam supply is throttled to a low value.

The above described conventional apparatus is made to control much better by forcing it to cycle the valve [2 open and closed in a manner to give time modulation of the steam supplied to the radiators and, because the steam valve is either fully open or closed, good distribution and proper condensate return will result. To cause this action, bellows 48 is suitably mounted on base 25 and is arranged to variably compress spring 49 to thereby exert a variable bias on arm 3|, the movement of bellows 48 being due to variations in the air pressure in said bellows, air being supplied to the bellows through a connection to nozzle 26 including a conduit 5| having a restriction 52 therein. To make the present apparatus cycle as intended, it is necessary that the change in bias efiected by maximum expansion of bellows 48 exceeds the normal operating differential of the controller, hence the bellows and spring 49 are constructed and arranged to insure this result. Restrictor 52 tends to delay the pressure changes in bellows 4B and thereby tends to increase the length of the on and off periods of the cycle. To further increase the length of these periods, a capacity tank 53 may also be connected to conduit 5| to thereby increase the amount of air that must flow through the restrictor 52 to effect a predetermined pressure change in the bellows.

While the arrangement of Figure 1 shows bellows 48 operating through spring 49 to adjustably bias the device by exerting a variable force on arm 3!, this bias may be imposed equally well by other mechanisms. For instance, in Figure 2, bimetal 32 is shown attached to a member 53 which is freely pivoted on pin 34 and is con.- nected to anchor plate 33 by a centering spring 64 coacting with a projecting tongue 5.5 of meme ber 63, this spring cooperating with projecting arm 86 of member 63 which engages one end at compression spring 31 to thus position member 63 relative to member 33. Spring 61 is adjusted by bellows d8 in the same manner as spring 49 in the above example. In this. modification, (33-. pansion of bellows 48 results in compression or spring 5'! and a biasing of arm 56 in a counter-.1 clockwise direction, thereby biasing bimetal 32 in the same direction as an increase in pressure in 48 in the apparatus of Figure 1.

Still another way of effecting a bias on the present controller is shown in Figure 3, wherein the like parts of this device are numbered the same as those in Figure 1. In this device, the nozzle assembly, the permanent magnet and the like are attached to a pivoted support member Hi, this mounting member being freely pivoted on pin 34 and held in an adjusted position by pin H coacting with cam slot 82 in member [3 which is rotatable about pivot 14 by the resultant force of bellows 48 and spring 6? acting on arm 15 of said member 13.. Expansion of bellows 48 rotates member 73 clockwise and causes, move-. ment of member 10 in a clockwise direction, While.

a contraction of said bellows permits spring 81 to cause motion of said members in an opposite direction. Thus, this apparatus changes the control point by shifting the position of the Valve. mechanism to thus change the working position of arm 3i. Because movement of member l8 and the attached Valve mechanism requires a reasonably flexible connection between branch air line 2! and member 10, loop 73 is provided, but any other suitable flexible connection means may be used. Neither of the latter two modifications show the capacity tank 53 used in Figure l but obviously such a tank may be used if desired.

Operation By ignoring bellows 48 in Figure l, it is apparent that the present apparatus will operate in a conventional manner, with bimetal 32; operating to move plate 21: away from nozzle 26; on a temperature drop, to thereby permit spring it to open valve l2, and; the element 32 will cause closure of said nozzle with a consequent closing of valve [2 on a temperature rise, both the opening and closing movements of the nozzle bein with a snap action because of; magnet 4i and its coacting armature 42. Further, due to the use of this snap acting means, the apparatus will tend to operate with a definite differential Whichis, for the purpose of this illustration, one degree.

Now, assume that bellows 48 is operative to change the control point of device 22 by a maximum of l as the pressure imposed on it varies from near zero to the maximum branch pressure, usually about 15 pounds per square inch. In the position shown, the pressure in bellows 48 is near zero due to the open nozzle 26 and the restricted air supply, spring 49 is exerting its minimum force and, assuming that device 22 would, without bellows 48, normally operate to open nozzle, 26 at 70 and would operate tov close said nozzle at 71, let it now be assumed that said device is responding to a temperature of slightly under 70".

With heat being supplied by radiator I due to open valve I2, the temperature rises and when the temperature reaches 71, bimetal 32 operates to close nozzle 26. This causes pressure to build up in branch line 2| and motor I6 to close valve I2. Also pressure starts building up in bellows 48 which tends to expand and increase the force exerted by spring 49. When the additional force exerted by spring 49, due to the expansion of bellows 48, is suiiicient to bias arm 3| of device 22 by an amount equivalent to about a one degree shift in control point, said arm is forced to the right just as though the device is responding to a 70 temperature. This opens nozzle 26 and permits valve I2 to open and supply more heat. Simultaneously, the pressure in bellows 48 starts bleeding down and the bias exerted by spring 49 is lessened. As the space temperature was 71' when this last operation was initiated, it may be considered that the temperature will now rise slightly, so the pressure in bellows 48 must bleed almost down to its previous value before bimetal 32 is able to force arm 3I to the left, thereby closing nozzle 26 and again closing valve I2. As before, closing nozzle 26 and the resulting building up of branch line pressure causes bellows 48 to again expand and increase the bias exerted by spring 49. However, assuming that the space temperature has risen still further, more bias is required this time than the time before to move arm 3| to a valve opening position, hence the pressure must build up to a higher value in said bellows and, as thi pressure build up requires time due to restriction 52 and capacity tank 53, this off period for the apparatus is longer than the previous one. However, when the pressure rises high enough in bellows 48 so that the actual temperature minus the bias amounts to 70, nozzle 26 is opened as before, with a consequent opening of valve I2 and the supplying of more heat. Also, the pressure starts bleeding down from bellows 48 again, but this time it need not reach as low a value as before for, since the space temperature has risen somewhat, the added force of bimetal 32 is able to overcome more bias than before and still exert a force similar to what it would normally exert at 71 and thus again close the nozzle. This last cycle had a, longer off period than before because a greater bias was required to force nozzle 26 open, and the on period was shorter than before because less of the bias had to be removed before nozzle 26 could be closed by bimetal 32. It should be noted that the rate of pressure build-up in bellows 48 diminishes as the pressure in said bellows approaches the branch line pressure, due to the diminishing pressure drop across restriction 52, and the rate of pressure drop in bellows 48 is initially high, due to the large pressure drop across the restriction, and gradually decreases as 6.. thebellows pressure approaches a branch line pressure of near zero. Thus, when bellows 48 is operating near its maximum pressure level, the pressure, and the increase in bias, builds up relatively slowly, and the pressure bleeds down rapidly, thus rapidly diminishing the bias. Likewise, when relatively low pressures are impressed on said bellows, the bias increases rapidly and decreases slowly. This tends to give long off periods and short on periods and when a large bias is used, and smaller bias gives shorter off periods and longer on periods. When the space temperature rises slightly above 71 /2 degrees, and nozzle 26 is closed, even the maximum bias of 1 /2 degrees cannot force said nozzle open against the force of bimetal 32, hence 71 degrees rather than 71 degrees is now the upper limit of the control range of the present apparatus and valve I2 remains closed.

If the temperature should now go below 71% degrees, the 1 degrees bias is sufficient to over-' come bimetal 32 and operate to open nozzle 26, thus supplying heat until the open nozzle bleeds down thepressure in bellows 48 sufficiently to diminish the bias to a value such that the resultant force on arm 3I is again equivalent to '71 degrees affecting bimetal 32, at which point said arm breaks away from the position shown and spring 29 forces plate 2! against nozzle 26 to thus start another off period which will continue until the bias increases enough to give the effect of a '70 degrees temperature at bimetal 32, with a resulting opening of the nozzle. Thus, the present apparatus cycles on a decrease in temperature in the same manner as when the temperature was increasing.

If the temperature should continue to decrease until it reaches 71 degrees or less, nozzle 26 will remain open as will valve I2 for, even with no bias, 71 degrees at bimetal 32 is required to snap arm 3| from the position shown to its opposite nozzle closed position. As there is nothing capable of closing nozzle 26 when the temperature is below 71 degrees, it remains open continuously, hence 71 degrees is now the lower limit of the operating range of the present apparatus and valve I2 remains open. Obviously, if the temperature should be slightly above 71 degrees,zthe pressure in bellows 48 would have to bleed nearly to zero to thus remove nearly all of the bias before bimetal 32 could close nozzle 26, thus causing a long on time and, upon closingthe nozzle, the pressure would build up to cause a bias of slightly over a degree relatively rapidly, thus giving a short off period.

I Obviously, in the apparatus shown, spring 49 exerts a force even when the pressure in bellows 48 is at a zero value hence the bias referred to is perhaps more properly called a change of bias. However, the net effect of the change in force or change in bias is exactly the same as if a bias be imposed, varied, or removed, hence there should be no difliculty from the terminology used.

The operation of the modification shown in Figure '2 is exactly the same as that of Figure 1, with the exception that the bias is imposed by moving bimetal anchor plate 63 slightly against spring 64 as. the pressure builds up in bellows 48 and compresses spring 61 instead of imposing the bias directly on blade 3I, the operation otherwise being the same. While Figure 2 does not show a capacity tank 53 in parallel with bellows 48, it is'obvious that such a tank can be used ifthe timing requirements necessitate it.

Likewise, the apparatus of Figure 3 is similar in function to that of Figure 1 excepting thebias tively stationary, movement of support member it to the left will cause valve plate 21 to engage 3i and open nozzle 26 to bleed out air in the same manner as previously described. Then, as the air pressure diminishes in the branch line and bleeds from bellows 48 through restrictor 52 due to the open nozzle, spring 61 then tends to force member back toward the right by rotating member I3 counterclockwise to thereby remove the efiective bias. Thus, the modification of Figures 2 and 3 diifer in mechanical detail only and are functionally similar to Figure 1. While the apparatus herein shown involves pneumatic equipment and the biasing force is exerted as a function of branch line pressure, and with a suitable time delay, it is obvious that other arrangements may be used provided a two-position controller is involved and the bias is exerted under control of the controller and is somewhat retarded in effect, and wherein the bias may exceed the normal operating differential of the device.

This invention is not limited to temperature controlling equipment, and an application to humidity control will now be explained.

Figure 4 In Figure 4, water is supplied through pipe Tl under control of valve 18 to a plurality of atomizer heads 19, the water being supplied under sufiicient pressure to finely atomize it for increasing the humidity in the space being treated, such as in a textile mill. Valve 1'8 is conventional and includes a body 80, a movable valve member Bl, a spring 82 for moving the valve member 8! in an upper and closed position, and a pneumatic motor 83 for driving the valve member 8! to a lower open position. The air for operating motor 83 is furnished from a suitable source, as before, through pipe 84 and restrictor 85 to branch line air conduit 86. The branch line pressure is controlled by humidistat 8'! which includes a base member 88 and a hair element 89 connected to a pivoted arm 90. Arm 9G is adjustable by an eccentric 9i which is attached to an anchor plate 63 freely pivotal on pivot 3 An upstanding arm 55 of plate 63 is biased clockwise by a spring 54 reacting against a flange of a member 33, said member being frictionally held on pivot 34 and moveable by adjustment handle 35. Arm 65 of member 53 is urged counterclockwise, and against the bias of spring 64, by spring 6'! which reacts against bellows 48. With this arrangement, adjustment of 35 varies the bias of spring 6t, thus causing a new equilibrium position for member 63 and cam 91 and thus a new working position for element 89 and, likewise, a variation in the pressure in bellows 4B and a corresponding change in the force exerted by spring 61 will vary the working position of element 89, and thus shift the control point of the device in a manner similar to the device of Figure 2. The other end of element 89 is attached to a spring 93 and to bell crank 94 pivoted on a stationary pin 95 and having an upwardly extending valve plate operating portion 96. Spring 93 keeps element 89 under a substantially uniform tension at the control point and furnishes the force for operating lever counterclockwise when element 89 elongates or is shifted. The controller valve mechanism of this device is similar to that previously described and includes nozzle 26 attached to base 88 by a supporting flange 40, and a nozzle or valve plate 22 is pivotally connected to this mounting flange by pivots 28, only one of which is shown. Valve plate 21 is held against nozzle '25 by a spring 29. To provide snap action for the present valve mechanism, a soft iron armature 42 is attached to plate operating member 98 and coacts with a small permanent magnet M in the same manner as in the previously described examples, the proximity of the armature to the magnet being limited by stop screw 38 coacting with stop flange 39. As the biasing means used in this example is similar to that used in Figure 1, it is numbered in a similar fashion, as above noted.

In describing the operation of this apparatus, it may be assumed that, with zero pressure in bellows i8, spring 53 tends to rotate lever 9 counterclockwise and the magnetic attraction of elements M and 42 and the tension of hair element tend to rotate bell crank E i clockwise, this latter rotation being limited by stop screw 38 engaging stop flange 39. Further, when valve plate 21 is in an open position, spring 29 also assists in moving portion 96 in a clockwise direction. Assuming now, for instance, that with zero pressure in bellows 48, the present instrument has an operating differential of about 4% relative humidity and is adjusted so that, with a relative humidity of 50%, the apparatus is in the position shown, the branch line air pressure is near 15 pounds per square inch, valve i8 is open and water is being sprayed from atomizer heads 19. This will tend to increase the relative humidity and, as it increases, hair element 89 tends to expand and, when this expansion is a result of a 4% increase in relative humidity, the normal bias of spring 93 is suificientto force member 96 to the left against the magnetic attraction of elements 4| and 42, the pull exerted by element 39 and the force of spring 29 to thereby force plate 2? away from nozzle 26 and bleed the branch line pressure down to near zero. Bleeding down the branch line pressur permits valve 18 to be closed by spring 82, thereby stopping the flow of Water from the atomizer heads and permitting the relative humidity to again diminish.

The contraction of hair element 88 as the humidity again decreases causes bell crank 9A to rotate clockwise and permit the closing of valve plate 21 against nozzle 25, this action taking place positively due to the efiect of the magnet snap mechanism. If it now be further assumed that the bias efiected by bellows 48 having 15 pounds of air therein amounts to the equivalent of 6% change in relative humidity, it appears that the pressure in bellows 48 will vary towards 15 pounds when nozzle plate 21 engages nozzle 26 and the branch line pressure is at 15 pounds. However, as pressure builds up in bellows 48 and the bias of spring 6! is increased, the effect of this bias, added to the effect of the actual relative humidity on element 89, tends to exceed the 4% relative humidity, in effect, needed for opening nozzle 28 and this effective value will be reached before the pressure in bellows 48 reaches 15 lbs. per square inch. Starting with an actual 50% relative humidity, only /3 of the maximum bias changing ability of bellows 48 needs to be used to open nozzle 25 hence, as the pressure builds up in bellows 48, element 89 is shifted downward, permitting spring 93 to cause valve plate 21 to move nozzle 26, thereby bleeding the branch line pressure to near zero and causing valve 18 to close. The open nozzle 26 not only bleeds down the branch line as before but also bleeds the air out of bellows 48, thereby diminishing the bias and moving element 89 upwardly toward its former working position. It was previously assumed that there was zero bias from bellows 48 with the apparatus in the position shown but this is obviously only a preliminary assumption because, with the valve plate closed against the nozzle, a maximum bias tends to result. Assuming that a resultant relative humidity of 54% is required for opening the nozzle, then it is obvious that it can be opened at an actual relative humidity of about 48% for the 48% plus the 6% equivalent of bias equals the 54% required to open the valve member and, if the relativ humidity should fall below 48%, then the nozzle cannot be opened because, even with a 6% equivalent bias, the necessary 54% resultant cannot be attained. Therefore, 48% appears to be the low end of the relative humidity range of this apparatus, as adjusted.

If the actual relative humidity should now rise above 50%, it is apparent that valve member 21 cannot be closed against nozzl 26, for the bias of spring 93, even with zero pounds pressure in bellows 48, is sufficient to hold this valve member open, it being previously noted that an equivalent of 50% or lower relative humidity was required to close the nozzle plate. Therefore, 50% becomes the upper value of relative humidity to be controlled by this apparatus, and intermediate values, such as between 48% and 50%, will result in the present apparatus cycling on and off in the same manner as in the previous examples.

This intermittent operation of controller 86 and water valve I6 provides a good control arrangement for atomizer heads because they are either supplied with water at full pressure or the water is turned off, hence a proper spray is obtained when needed. Also, for the reasons explained in the previous example, the on periods tend to be short and the off periods long as the upper value of humidity is approached and the on periods are relatively long and th oil periods relatively short as the lower value is reached. Further, when the relativ humidity is above the upper end of the operating differential of the apparatus, the spray heads are maintained continuously off and when the humidity is below the lower end of the differential, the heads are maintained in continuous operation.

3 This invention also has utility for controlling pressure in a system having a relatively large volumetric capacity and wherein modulation of the flow valve controlling said pressure is not desired for one reason or another. An example of a control arrangement of this sort is shown in Figure 5.

Figure In Figure 5, steam is fed into the jacket of a cooking kettle or the like, not shown, through pipe I I I from a suitable source II2 under control of valve II3, this'valve being of the normally open sort wherein valve member H4 is held in an upper open position by spring I I5 and is driven to a lower closed position by pneumatic motor II6. line II1 which is connected to main H8 through restrictor II9, with branch line pressure depending upon the operation of pressure controller I20. Controller I20 includes a housing I2I to which is attached a bellows I22 connected to Motor H6 is supplied air from branch pipe III by a tube I23, bellows I22 thereby responding tothepressure controlled by valve I I3. The pressure exerted by the bellows I22 is transmitted through a strut member I25 against a lever member I24 pivoted at I21 and urged in a clockwise direction by spring I28, bellows I22 operating to move the lever member I24 in a counterclockwise direction. Arm I26 of member I24 is'used to operate a valve mechanism similar to that previously described and which is provided with a similar magnet snap mechanism, the apparatus being so arranged that arelatively high pressure in pipe III causes counterclockwise rotation of I26 until stopped by stop screw 38 engaging stop flange 39, this permitting spring 29 to close valve plate 21 against nozzle 26 and building up branch line pressure sufficient to drive valve member II4 to its lower closed posi tion, thereby permitting the controlled pressure to diminish. A relatively low pressure permits spring I28 to rotate lever I 26 in a clockwise direction and thus permits arm I26 to lift valve plate 21 away from nozzle 26, thereby bleeding the branch line pressure down and permittting spring II6 to open valve II3 and permit flow from the supply line II2 through pipe III.

To cause cyclic operation of valve II3, bellows 48 and spring 61 are connected through conduit 6| and restrictor 52 to the branch line, in the same way as before, so that, when nozzle 26 is closed by plate 21, pressure builds up in bellows 48 and increases the'bias on lever I26 by compressing spring 61, this having the effect of tending to rotate lever I26 in a clockwise direction to again move plate 21 away from nozzle 26 to permit an opening of valve II3. Opening valve II3, of course, increases the pressure in III and therefore increasesthe force exerted by bellows I22 tending to drive lever I26 in a counterclockwise direction. Also, when nozzle plate 21 is moved away from nozzle 26 so that the branch line pressure is reduced, the bias exerted on lever I26 by bellows 48 is also diminished and I26 tends to move back to the position shown.

Without assuming values of differential for the normal operation of this pressure controller and then assuming a larger bias value for bellows 48, suflice it to say that the effect of the variable bias on the controller in this example is precisely the same as in the previous example and results in, what normally would be the lower limit of a particular setting becoming the upper limit and the actual lower limit being displaced downwardly from that value by an amount equal to the difference .of the maximum bias and the normal diiferential, as previously explained. Likewise, at intermediate values of pressure, the apparatus will cycle on and oif with the length of the respective on and off periods depending upon whether an upper or a lower limit is being approached.

In addition to being useful for controlling steamflow to cooking kettles, or other such use wherein the pressure changes relatively slowly as the control valve is opened or closed, this arrange- .ment maybe used for refrigeration control wherein valve II3 is in series with a fixed expansion device such as an orifice or small tube, not shown,'bellows I22 being connected to the low pressure side .of the expansion device.

. As previously pointed out, the examples given above are merelyillustrative, and many substitutions and equivalents are readily visualized by one skilled in the art. For instance, other formsof snap acting mechanism may be used,

other'pneumatic valve-arrangements may be used and it is not even necessary'that this apparatus be pneumatic in operation so long as the bias gradually varies in amount and may exceed the normal operating difierential of the instrument. Also, if desired, a two position non-bleed valve may be used in the controller instead of the bleed valve shown. Because of the many substitutions and equivalents readily perceived by those skilled in the art, I wish to be'limited only by the appended claims.

I claim:

1. In a conditioning system having a conditioning element, a conduit for delivering conditioning medium to said element from a suitable source, valve means for controlling flow through said conduit means, pneumatic motor means for operating said valve means, controller means responsive to-a condition varied by said element, branch conduit means connecting said controller to said pneumatic motor means, air supply means also connected to said conduit means, said controller including an adjustable motor means connected to said conduit means and arranged to continuously adjust said controller by a predetermined amount when the pressure in said branch conduit is at its maxium value and a lesser amount when said branch conduit pressure is at a lower value, air flow delay means in said connection between said adjusting means and said branch conduit means, said controller including a pneumatic valve means definitely movable to either a fully open position or a fully closed position as said condition responsive means responds to changing values of said condition, the difference in condition values required to operate said valve means from one position to the other being less than the maximum adjustment provided by said adjusting motor.

2. Pneumatic control apparatus for a temperature changing system having temperature control means operable to on and off positions, a pneumatic motor means for controlling the temperature control means, a controller for said motor means including a device responsive to temperature in a space being treated, said controller also including valve means operable by said device, said valve means being connected to said motor means and arranged to control the air pressure imposed on said motor means, mechanism for causing operation of said valve to one or another of two positions upon temperature changes within the control range of said apparatus, said mechanism tending to cause said controller to operate with a predetermined differential, adjustable continuously active biasing means including a relatively small pneumatic motor arranged to adjust said controller, and conduit means including a fiow restriction connecting said small motor to said controller valve means; said biasing means being capable of. adjusting said apparatus by an amount exceeding said differential.

3. Control apparatus for a steam heating system having heat control means operable to on and oil positions and having a motor means for actuating said control means, a controller for said motor means including, a device responsive to temperature in a space being heated by said system, said controller also including control means operable by said condition responsive device connected in controlling relation to said motor means, mechanism for causing operation of said control means to one of two positions by said condition responsive device upon temperature changes-in said space within the controlling range of said apparatus, continuously active force exerting adjustingmeans connected to said control means and capable of adjusting said apparatus by an amount greater than the temperature change normally required to cause operation of said control means from one position to another position, and time delay means arranged to de lay the response of said force exerting adjusting means upon a position change of said control means, the force exerted by said adjusting means thu being dependent on the time elapsing after operation of said control means and the functioning of said time delay means.

4. A humidity control system comprising a spray nozzle; a supply of water under pressure connected to said nozzle; a valve for controlling said supply; a motor for actuating said valve, and a controller connected in controlling relation to said motor, said controller including a force exerting element responsive to humidity, a control device arranged to be operated by said humidity responsive element and capable of controlling said motor, snap acting means arranged to cause two-position operation of said device by said element, force exerting biasing means arranged to continually adjust the operative relationbetween said device and said element, said biasing means being variably operable in accordance with the operative position in said device, and means for delaying the response of said biasing means to a changed position of said device.

5. In a pressure controlling system, pneumatic motor means arranged to actuate a pressure changing device, a controller for said motor means, said controller including means responsive to pressure and-a pneumatic valve means operable to be opened or closed by said pressure responsive means upon variations in pressure, snap action means for causing said valve means to be operated to either a closed or'fully open position, said controller requiring a predetermined difierence in pressure to operate said valve means from one position toanother position, conduit means connecting said valve means to said motor means, and-force exerting second motor means connected to said conduit means and arranged to continual- 1y adjust saidcontroller in a direction to cause said valve means to be driven to its opposite positlon by variations in its force, said second motor means being capable of adjusting said controller by an amount exceeding the value of. said predetermined dilference.

6. In a pnuematic controlling system, pneumatic motor means arranged to actuate a condition changing device, a controller for said motor means, said controller including force exerting means responsive to the condition being controlled and a pneumatic valve means operable to an open or closed position by said condition responsive means upon variations in said condition, snap action means for causing said valve means to be operated to either a closed or fully open position, conduit means connecting said valve means to said motor means, said controller requiring a predetermined difference in said condition to operate said valve means from one position to another position, and second force exerting motor means connected to said conduit means and arranged to adjust said controller in a direction to cause said Valve means to be driven to its opposite position by variations in its force due to variations in pressure in said conduit, said second motor means beingcapable of adjusting said 13 controller by an amount exceeding the value of said predetermined difference.

'7. In a, pnuematic condition controlling system; a device for changing said condition; motor means for controlling said device; pneumatic controller means for said motor means; conduit means connecting said controller means to said motor means; said controller means including a force exerting condition responsive means and a valve means arranged to be operated by said condition responsive means and connected to a suitable supply of air under pressure, said conduit means and to the atmosphere, snap acting mechanism for causing said condition responsive means to operate said valve means to one of two definite positions as said condition changes by a predetermined amount, resilient means arranged to bias said condition responsive means in one direction, a pneumatic motor means connected to said conduit means and constructed and arranged to adjust the 'bias exerted by said resilient means to thereby adjust said controller by an amount exceeding said predetermined difference of said condition and in a direction to anticipate a change in said condition, and adjustable time delay means for controlling the rate of response of said pneumatic motor means to variations in pressure of air in said conduit means.

8. Control apparatus for a steam heating system having heat control means operable to on and off positions and having motor means for actuating said control means, a controller for said motormeans including a force exerting device responsive to temperature in a space being heated by said system, said controller also including valve means operable by said condition responsive device connected in controlling relation to said motor means, mechanism for causing operation of said valve means to one of two positions by said condition responsive device upon temperature changes in said space within the controlling range of said apparatus, force exerting adjusting means connected to said valve means and capable of adjusting said apparatus up to an amount greater than the temperature change normally required to cause operation of said valve means from one position to another position, and time delay means arranged to delay the rate of response of said force exerting adjusting means upon a position change of said valve means.

9. A temperature controller comprising a pneumatic valve means, a temperature responsive means arranged to operate said valve means, snap acting mechanism arranged to cause operation of said valve means to either of two positions, said mechanism tending to require a predetermined difierential of temperature for operation of said valve means from one of its positions to its other position, and force exerting adjustable biasing means constructed and arranged for adjusting said controller by a variable amount which may exceed said differential, said biasing means including a pneumatic motor and conduit means including a flow restriction connectin said motor to said valve means, said flow restriction varying the rate of response of said biasing means to a change in said pneumatic valve means.

10. A humidity controller comprising a pneumatic valve means, a force exerting humidity responsive element arranged to operate said valve means, snap acting mechanism arranged to cause operation of said valve means to either of two positions, said mechanism tending to require a 14 predetermined difierential of humidity for operation of said valve means from one of its positions to its other position, and adjustable force exerting biasing means constructed and arranged for adjusting said controller by a variable amount which may exceed said differential, said biasing means including a pneumatic motor and conduit means including a flowrestrictor connected to said valve means, said flow restrictor controlling the rate of adjustment of said biasing means.

11. In a humidity controlling system, pneumatic motor means arranged to actuate a humidity changing device, a controller for said motor means, said controller including a humidity responsive element and a pneumatic valve means operable to open or closed position by said humidity responsive element upon variations in humidity, snap action means for causing said valve means to be operated to either a closed or fully open position, conduit means connecting said valve means to said motor means, said controller tending to require a predetermined difference in humidity to operate said valve means from one position to its other position, and second force exerting motor means connected to said conduit means and arranged to continuously adjust said controller in a direction to cause said valve means to be driven to its opposite position, said second motor means being capable of adjusting said controller by an amount exceeding the value of said predetermined difference.

12. A pressure controller comprising a bleedtype pneumatic valve means, a pressure responsive means arranged to operate said valve means, a snap acting mechanism arranged to cause operation of said valve means to either of two positions, said mechanism tending to require a predetermined difierential of pressure for operation of said valve means from one of its positions to another of its positions, and adjustable force exerting biasing means constructed and arranged for continually adjusting said controller by a variable amount which may exceed said differential, said biasing means including a pneumatic motor and conduit means with a flow restriction connecting said motor to said valve means, said flow restriction functioning to control the rate of adjustment of said controller by said biasing means.

13. A time modulating pneumatic pressure controller comprising a base, a pneumatic valve unit attached to said base, a pressure responsive device arranged to operate said valve unit, snap acting means arranged to insure two-position operation of said valve unit by said device, said snap acting means requiring a predetermined change in the operating force exerted by said deviceon said unit fOr operatin said unit from one position to another, force exerting biasing means arranged to variably adjust the operative relation between said device and said valve unit, said biasing means being capable of adjusting the operative relation of said element and units by an amount exceeding the effect of said predetermined change in force, and connecting means including a time delay means arranged between said valve unit and said biasing means for controlling the rate of adjustment effected by said biasing means in accordance with the operation of said valve unit.

14. A time modulating pneumatic humidity controller comprising a base, a pneumatic valve unit attached to said base, a humidity responsive element arranged to operate said valve unit, snap acting means arranged to insure two-position 15 operation of said valve unit by said element, said snap acting means requiring a predetermined. change in the operating force exerted by said element on said unit for operating said unit from one position to another, force exerting biasing means arranged to variably adjust the operative relation between said element and said valve unit, said biasing means being capable of adjusting the operating relation of said element and unit by an amount exceeding the eiTect of said predetermined change in force, and connecting means including time delay means arranged between said valve unit and said biasing means for controlling the rate of adjustment efiected by said biasing means in accordance with the operation of said valve unit.

15. A time modulating pneumatic thermostat comprising a base, a pneumatic valve unit attached to said base, a thermostatic element arranged to operate said valve unit, snap acting means arranged to insure two-position operation of said valve unit by said element, said snap acting means requiring a predetermined change in the operating force exerted by said element on said unit for operating said unit from one posi tion to another, force exerting biasing means arranged to variably adjust the operative relation between said element and said valve unit, said biasing means being capable of adjusting the operative relation of said element and unit by an amount exceeding the efiect of said predetermined change in force, and connecting means including time delay means arranged between said valve unit and said biasing means for causing operation of said biasing means in accordance with the operation of said valve unit, said time delay means controlling the rate of adjustment effected by said biasing means.

16. Control apparatus for a condition changing device operable by a pneumatically controlled motor movable between limiting positions, a controller for said device comprising an element arranged to exert a force variable in accordance with changes in a condition afiected by operation of said device, a pneumatic valve operable by said element, snap acting means for insuring that said valve will be operated only to closed or fully open position, a predetermined change in said condition being required to cause said element to move said valve from one position to another position, conduit means for connecting said valve to a suitable source of air and to said motor, second pneumatic motor means connected to said conduit means on the valve side of said restriction, and resilient means connecting said second motor means to said apparatus in a manner to continuously adjust the operative relation between said element and said valve, said pneumatic motor means being capable of adjusting said apparatus by an amount greater than the efiect of predetermined change of the condition on said apparatus.

FREDERICK D. JOESTING.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,162,170 Johnson Nov. 30, 1915 1,455,633 Lundgaard May 15, 1923 1,619,351 Lindsay Mar. 1, 1927 1,920,827 Wunsch Aug. 1, 1933 2,364,917 Ray Dec. 12, 1944 2,437,156 Frick Mar. 2, 1948 2,562,201 Merwin July 31, 1951

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